Fuse constructions including a gas filled reservoir



Aug. 23, 1966 R. E. FRINK ETAL FUSE CONSTRUCTIONS INCLUDING A GAS FILLED RESERVOIR E 3 2 I 8 1 4 J a \\\\\\\\\VJ K Q s m w@ i b 9 9 9 491/4 S 2 )Y I "v a o (Iv l M M 2 L RQQQX \v .M M m- Z S F 0 O 8 z 9 m a w M w smaaw w m 9 3 2 0 m j m 2am m wwmww z \\\\\v\\\ \\p\\\\\\\\\\\ A f A w A ll. w v 2 o 3 6 9 l L l C 0 d e H F INVENTOR Andrew Frey and Russell E. Frlnk BY M WITNESSES:

ATTORNEY Aug. 23, 1966 R. E. FRINK ETAL FUSE CONSTRUCTIONS INCLUDING A GAS FILLED RESERVOIR 2 Sheets-Sheet 2 Filed 001.. 11. 1963 RESISTANCE MATERIAL United States Patent 3,268,690 FUSE CONSTRUCTIONS INCLUDING A GAS FILLED RESERVOIR Russell E. Frink, Forest Hills Euro, and Andrew Frey,

Pittsburgh, Pa., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 11, 1963, Ser. No. 315,490 7 Claims. (Cl. 200-129) This invention relates to fuse constructions in general and, more particularly, to fuse constructions in which it is desirable to interrupt a wide range of current values.

The general object of the present invention is to provide an improved and highly-reliable fuse structure suitable for effectively interrupting currents over a relatively wide range of current values, yet is of simplified construction.

As well known by those skilled in the art, in expulsive-type fuses, in which an arc is drawn axially of a bore provided in a mass of gas-evolving insulating material wherein the structure is designed for the interruption of relatively high magnitude currents, by having an enlarged bore, there correspondingly results the difliculty of interrupting relatively low-value currents, wherein the small cross-sectional area of the arc stream does not afford an intimate enough engagement of the arc with the interior walls of the gas-evolving fuse-tube bore. As a result, during such low-current interruption, relatively little gas is evolved from the interior surface of the gas-evolving fuse-tube bore and, consequently, it may be difficult to extinguish such a low-value current. Consequently, the fuse may fail to interrupt relatively lowvalue currents because of the little gas which is evolved during such low-current interruption. Accordingly, it is another object of the present invention to remedy the foregoing defect and to provide an improved fuse construction in which a relatively large bore is available for the interruption of relatively high-magnitude currents and, in which, additional construction is provided for facilitating low-current interruption.

It is, therefore, another object of the present invention to provide an improved fuse construction which is particularly adapted for the interruption of low-value current, which are usually diflicult to extinguish, yet not sacrificing the good high-current performance of the fuse.

In accordance with one aspect of the present invention, a movable tubular reservoir constituting the arcing rod, and containing a compressed arc-extinguishing gas, is attached to the fusible element by a fusible connection, and, during fuse operation, the associated end of the movable tubular reservoir of the arcing rod is opened up to permit the ejection therefrom of the compressed gas. Such ejected gas is, of course, directed at the terminal end of the established arc, which is highly desirable during such low-current interruption, at which time the relatively small cross-sectional-area of the arc stream would have difficulty in contacting the inner surface of the gas-evolving fuse-tube bore suiiiciently to enable the evolution of the requisite quantity of gas necessary for interruption.

Still a further object of the present invention is the in a relatively high-voltage fuse structure.

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provision of an improved highly-reliable fuse-tube construction of exceedingly simple design and involving few easily replaceable parts.

An auxiliary object of the present invention is the provision of an improved fuse construction of the foregoing type which is adaptable for mounting in a dropout type of fuse mounting means.

Another object of the invention is to provide an improved trigger mechanism for a dropout type of fuse.

A further object of the invention is the provision of an improved fuse structure, suitable for high-voltage service, in which the formation of corona may be minimized.

In the United States patent application filed September 30, 1963, Serial No. 312,727, by Russell E. Frink, and assigned to the assignee of the instant application, there is disclosed and claimed the concept of utilizing a relatively large-diameter retractable arcing-rod construction It is, accordingly, a further object of the present invention to provide an improved fusible structure utilizing a relatively large-diameter arcing-rod construction to minimize the establishment of corona during operation in high-voltage service.

Additional objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

FIG. 1 is a side elevational view of a fuse structure embodying principles of the present invention, the fuse structure being shown in its intact operating condition;

FIG. 2 is a longitudinal vertical sectional view taken through the fuse-tube structure of FIG. 1, with the fuse element again being shown in its intact condition suitable for carrying line current;

FIG. 3 is a view similar to that of FIG. 2, but illustrating the position of the several parts during an intermediate part of the opening fusing operation;

FIG. 4 is a fragmentary enlarged sectional view illustrating the opening of the end of the gas-containing reservoir during fuse rupture;

FIGS. 5 and 6 show an alternate connection between the fusible element and the neck of the adjoining capsule reservoir;

FIG. 7 shows a modified type of fuse construction;

FIGS. 8 and 9 show rupture of the fuse element of FIG. 7 under low and high-current conditions respectively;

FIG. 10 illustrates a further modified type of fuse structure particularly suitable for low-current use; and,

FIG. 11 illustrates the operation of the kickout mechanism associated with the upper contact support of the fuse structure.

Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral 1 generally designates a fuse structure. As well known by those skilled in the art, the fuse structure :1 may comprise a supporting means, in this particular instance including a pair of stand-01f insulators 2, 3 having associated with the extremities thereof terminal means 4, 5. The terminal means 4 comprises a releasable kickout mechanism, generally designated by the reference numeral 6, and set 3 forth more clearly in the United States Patent 2,403,121, issued July 2, 1946 to Herbert L. Rawlins and John J. Mikes, and assigned to the assignee of the instant application.

Electrically interconnecting the two terminal means 4, 5 is a fuse-holder assembly, generally designated by the reference numeral 7 and comprising a fuse tube 8, the internal construction of which is more clearly shown in FIG. 2 of the drawings.

As well known by those skilled in the art, the fuse tube 8, with the associated ferrules 9, 10 has fixedly secured thereto suitable hardware items, such as a hinge support 11, guided in a slot 12 of the lower terminal means 5, and a pullout ring fixture 14 suitable for cooperation with a hook-stick for effecting opening or closing movement of the fuse structure 1.

With reference to FIG. 2 of the drawings, it will be observed that disposed interiorly of the fuse tube 8, which may be composed of a suitable insulating material of the requisite structural strength, is a metallic guide tube 15 having reciprocally movable therein a pulley assembly 16 biased to an upward retracted position by a compression spring 17. The compression spring 17 seats, at its lower end, against the upper end of a lower-disposed arcing tube 19 and bears at its upper end against a spring seat 20 having an actuating pin 21 movable therewith, and projecting through an opening 22 of the ferrule 9 to effect actuation of the kickout mechanism 6, as more fully described hereinafter.

As shown in FIG. 2, the arcing-tube portion 19 has disposed interiorly therewithin a gas-evolving liner 23 composed of a suitable gas-evolving material, such as boric acid, or horn fiber. Preferably, the gas-evolving liner 23 provides a fuse bore 24, through which is drawn and lengthened the are established by fusing of a fusible element 25. As shown, the fusible element 25 is fixedly secured at its lower end to a terminal rod 26 connected to a spider support 27, the latter being suitably secured between a metallic corona shield 28, and a lower support sleeve 29.

Fixedly secured, as by a soldered joint 30, to the upper end of the fusible element 25 is a movable tubular reservoir, or retractable arcing rod 31 containing a suitable arc-extinguishing gas under pressure therewithin, such as carbon dioxide (CO or sulfur hexafiuoride (SP gas under pressure. The soldered joint 30 may be composed of any desired fusible material, such, for example, as silver, zinc, tin, or alloys thereof. The movable cartridge, or capsule 31 is fixedly secured at its upper end to a cable 32, which passes over a pulley 33, and is secured, as at 34, to a support rod 35.

It will be apparent that following fuse rupture the compression spring 17 will be effective to cause upward movement of the spring seat 20 and hence retraction of the cable 32, carrying therewith the movable tubular arcing rod, or cartridge 31 to an upper position, as indicated more clearly in FIG. 3 of the drawings.

More particularly, with reference to FIG. 4, the passage of relatively low overcurrents through the fuse structure, in excess of its rating will generate heat within the fusible element 25 and will melt the fusible joint 30, thereby permitting the separation between the fusible element 25 and the tubular arcing rod 31 drawing the arc 18. This will provide an opening 36, as shown in FIG. 4 at the end of the capsule 31, and will cause the ejection of a quantity of arc-extinguishing gas, contained within the movable cartridge 31, into the arcing region 37 (FIG. 4) to thereby facilitate arc interruption. This is particularly desirable during low-current interruption when, due to the small cross-sectional area of the arc stream 18, there results little intimate engagement between the are 18 and the inner surface 23a of the gas-evolving liner 23. During the occurrence, of such relatively low-current arcs the provision of the movable tubular cartridge 31, containing a dielectric gas under pressure, will permit the rapid extinction of such low-current arcs 18, which otherwise would prove to be a problem.

For currents of higher value, not only will the fusible joint 30 melt, but the fusible element 25 will disintegrate generating even more heat than in the previous case. For even larger interrupting currents, say, for example, those over 500 amperes, it is immaterial whether or not the capsule is opened, since disintegration of the fuse link 25 and drawing a large-amperage are 18 along the fuse bore, as shown in FIG. 3, will generate an adequate amount of gas from the gas-evolving liner 23 itself, to the exclusion of capsule activity.

It will, therefore, be apparent that during heavy-current interruption, as during the occurrence of heavy fault currents of large amperage, in the circuit protected by the fuse structure, there will be a sufiicient intimate engagement between the arc 18 and the inner surface 23a of the fuse-tube lining 23 for the production of the requisite amount of arc extinguishing gas.

The opening retracting movement of the spring seat 20 and the associated actuating pin 21 will cause the ejection thereof through the opening 22 of the ferrule 9 to effect unlatching of the kickout mechanism 6, as illustrated in FIG. 11 of the drawings.

More particularly, the terminal means 4 includes a housing shield 43 having pivotally supported therein an ejector casting 44 biased in a counterclockwise direction about a stationary pivot pin 45 by an ejector spring 46. A trigger 47 pivotally mounted on the ejector casting 44 normally is seated on a ledge 43a and is released therefrom by ejection of the trigger rod 21 through opening 22 of the fuse holder 7, as clearly set forth in US. Patent 2,403,121. Drop-out operation of the fuse-holder assembly consequently takes place for fuse indication and the provision of an isolating gap.

FIGURE 5 shows a modified type of neck portion 40 for the capsule, which is of relatively smaller dimensions than the neck portion 31a of the capsule construction illustrated in FIG. 4. As a result, the heat of fusion of the fusible element 25 is sufficient to burn off the lower tip of the neck portion 40, thereby opening up the lower end of the modified-type capsule 41 and permitting the ejection of the compressed gas thereof through the opening 36a, as shown in FIG. 6.

FIG. 7 illustrates a modified type of fuse structure in which a fuse element 50 comprises a telescopic connection 51 between two tubes 50a, 50b. Preferably, a low-melting-temperature solder, such as a lead alloy 52, is interposed in the joint between the fuse tubes 50a, 50b. Such a construction would be suitable, for example, for a normal current rating of 7 to amperes. During lowcurrent interruption, the solder 52 melts, the tubes 50a, 50b pull apart, and compressed fluid is ejected through the opening 36 of the capsule 60, as shown more clearly in FIG. 8 of the drawings.

FIG. 9 shows the interruption of heavy currents in the modified type of fuse construction of FIG. 7, where the fuse element 50 fuses entirely, and receives a blast of fluid out of the opening 36, in addition to receiving a blast of gas evolved from the gas-evolving liner 23. For extremely low current (.5 to 5 amps) some means of additional heating is required to produce adequately high temperature at the solder joint for melting the solder alloy. This may be accomplished by means of a heatproducing auxiliary resistance disc, made out of compressed graphite, because decreasing the wall thickness of the tubular fuse element further may become technologically impossible. This would be necessary to increase the resistance of the fuse element, to produce adequate heat at low currents for melting the solder alloy.

FIG. 10 shows such a modified construction suitable for very low-current use, i.e. having, for example, a normal current rating of, say, /2 ampere to 5 amperes. A resistance disc 53, composed, for example, of a carbonimpregnated material is interposed between a conduct ng sleeve 54 and the fuse element 50 to generate sufficient heat to effect separation of the fuse tubes 50a, 50b. High-current interruption, on the other hand, will immediately disintegrate the entire fuse element 50, as was the case illustrated in FIG. 9. The lower end of the conducting sleeve 54 is connected, by any suitable means, to the lower ferrule of the fuse structure. In such a case, the terminal rod 26 would be omitted.

From the foregoing description of the invention, it will be apparent that there is provided an improved fuse structure in which a movable tubular electrode, or cartridge 31, is movable with the fused end of the fuse link during a fusing operation, and operable to cause the ejection of a compressed dielectric fluid into the arcing space 37 and interiorly of the arc passage to facilitate arc interruption. Such action is especially desirable during low-current interruption. During relatively high-current interruption, the cross-sectional area of the arc 18 is sufficient in itself to evolve an adequate amount of gas from the inner surface 23a of the fuse liner 23 within the fuse bore 24.

The present invention provides an improved fuse structure, suitable for high-voltage service, in which the formation of corona and its corrosive by-products (nitrous acid) may be prevented. As well known by those skilled in the art, electric corona occurs when the electrostatic flux density on the surface of a conductor exceeds the electrostatic strength of the air (approximately 21.1 kv./cm.). At a given voltage, corona is determined by conductor diameter, line configuration, type conductor, condition of its surface, and also the weather. As a result of corona, a chemically-active gas, ozone is produced, which, in the presence of moisture, produces nitrous acid, a highly corrosive agent, which may cause excessive damage of the fuse element, as well as other points of the fuse structure. In a fuse adapted for highvoltage service, such as described herein, the diameter of the fuse rod must be such, that the electrostatic field intensity does not exceed the breakdown voltage of the air in order to prevent corona and its accompanying corrosive by-products. The fuse construction described in the present invention utilizes a long, tubular rod filled with are extinguishing gas which escapes from the tube into the area containing the arc during low-current interruption. This improved ability of the fuse to interrupt low current permits the utilization of a large bore and also permits the fuse-rod diameter to be greater than the minimum required diameter to prevent corona at voltages up to 115 kv., and higher thus preventing the formation of corrosive agents such as nitric acid, and provides a more reliable corona damage-free high-voltage fuse structure. For 69 kv. service, it is recommended that the fuserod diameter be inch, and for higher voltages the diameter of the fuse rod 31 should be /2 inch.

Although there have been illustrated and described specific fuse structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may be readily made therein by those skilled in the art, without departing from the spirit and scope of the invention.

We claim as our invention:

1. A fuse structure comprising an'elongated tubular, movable, conducting fuse terminal constituting a movable reservoir containing a compressed arc-extinguishing fluid, said movable fuse terminal reservoir having an openable end, fuse-link means mechanically and electrically connected to said openable end of the movable fuse terminal reservoir, said tubular fuse terminal forming the only conducting path leading away from the fuse link in one direction, whereby the passage of fault current through the fuse structure will fuse the fuse-link means so that the heat of fusion will open up the openable end of the movable fuse terminal reservoir to release the compressed arc-extinguishing fluid to assist in arc-extinction and means for separating the fused ends of the fuse link upon fusion of the fuse link and for moving the fuse terminal axially.

2. A fuse structure including a movable, tubular, elongated conducting fuse terminal rod, a fuse link electrically and mechanically connected to one end of said elongated movable fuse terminal rod, compressed-fluid reservoir means comprising, at least in part, said tubular elongated fuse terminal rod, the extremity of said movable fuse terminal rod close to the point of attachment of said fuse link having an openable end portion which is opened upon fusion of said fuse link by the passage of overload current therethrough, means for actuating said fuse terminal rod to move and to separate the fused ends of the fuse link upon the fusion of the fuse link, said fuse terminal rod comprising the only conducting path leading away from the fuse link in one direction, and guiding means for directing the released blast of compressed fluid against the established arc to assist in effecting the extinction thereof.

3. A fuse structure adaptable for interrupting a wide range of currents including gas-evolving fuse-tube bore means, the inner wall of which at least partially evolves gas upon subjection to the heat of an arc, a movable, tubular, conducting arcing rod movable axially through said bore means and containing, in reservoir-like fashion, a compressed dielectric fluid suitable for arc-extinction purposes, a fuse link connected at one end by a fusible connection to an extremity of said movable tubular arcing rod, said movable tubular arcing rod comprising the only conducting path leading away from said one end of said fuse link, said extremity of the arcing rod having an openable end opened by the heat of fusion of the fuse link, and biasing means for actuating said movable arcing rod axially through said gas-evolving bore means upon fusion of the fuse link for combined arc-extinguishing action.

4. A fuse-tube structure including an elongated fuse having an exhaust chamber at one end and a gas-evolving arc passage disposed adjacent thereto, a fuse link supported in said exhaust chamber, an elongated, movable, tubular, conducting arcing rod containing a compressed arc-extinguishing fluid and connected by a fusible connection at one end to one end of said fuse link, said tubular arcing rod forming the only conducting path leading away from the fuse link in one direction, and arcing-rod biasing means for actuating said arcing rod axially along said gas-evolving arc passage in a direction away from the exhaust chamber upon the fusion of the fuse link, whereby fusion of the fuse link will release said arcing rod for axial movement along said gas evolving arc passage, fuse said fusible connection and open up the end of the tubular arcing rod to release a blast of arc-extinguishing gas to facilitate ar-c extinction.

5. In combination, fuse structure including an elongated fuse tube having a gas-evolving liner, said gasevolving liner constituting an arc passage having an axial bore, a tubular, conducting fuse-terminal assembly movable axially along said gas-evolving arc passage and normally forming the only conducting path through the gas passage, said tubular movable fuse-terminal assembly forming a movable reservoir containing a compressed arcextinguishing fluid and having an openable end, a fusible element mechanically and electrically connected to the openable end of the movable reservoir, and means for actuating the fuse-terminal assembly axially along the gas evolving arc passage upon fusion of the fusible element, whereby the heat of fusion generated upon fusing of said fusible element will open up said end of the movable reservoir and cause thereby an ejection of compressed arc-extinguishing fluid through said openable end to play upon the terminal end of the established arc to assist in the rapid extinction thereof.

6. Fusible means including a compressed-fluid capsule having a neck portion with one end of a fuse tube inserted therein, a second fuse tube telescopically related to the other end of the first said fuse tube, the two fuse References Cited by the Examiner tubes having a slidable joint therebetween, and fusible UNITED STATES PATENTS material in the interface region of said joint, whereby upon the attainment of a predetermined current magni- 8251879 7/1906 Delsenhofertude said fusible material will melt and the telescopically- 5 1,530,264 3/1925 Hope X related fuse tubes will pull apart and separate to draw 2,263,745 11/1941 Srokz} 200-117 an arc therebetween, both of said fuse tubes being adapted 2,343,422 3/1944 Rawllps 200 120 to fuse upon the occurrence of relatively high currents 2,403,121 7/1946 RPWImS at 2OO 117 therethrough. 2,571,735 10/1951 Llndell 20O12O 7. The combination of claim 6, wherein a series re- 10 2,821,602 1/1958 Hordechuck ZOO-123 sistance disc is disposed adjacent said slidable joint to increase the heating effect for a low-current fuse rating. BERNARD GILHEANY P'imary Examiner 

1. A FUSE STRUCTURE COMPRISING AN ELONGATED TUBULAR, MOVABLE, CONDUCTING FUSE TERMINAL CONSTITUTING A MOVABLE RESERVOIR CONTAINING A COMPRESSED ARC-EXTINGUISHING FLUID, SAID MOVABLE FUSE TERMINAL RESERVOIR HAVING AN OPENABLE END, FUSE-LINK MEANS MECHANICALLY AND ELECTRICALLY CONNECTED TO SAID OPENABLE END OF THE MOVABLE FUSE TERMINAL RESERVOIR, SAID TUBULAR FUSE TERMINAL FORMING THE ONLY CONDUCTING PATH LEADING AWAY FROM THE FUSE LINK IN ONE DIRECTION, WHEREBY THE PASSAGE OF FAULT CURRENT 